Solder bumps are used for electrical connection between package substrates and IC chips. Solder bumps are generally formed in the following processes:
(1) A process to print flux on a connection pad formed on a package substrate.
(2) A process to mount solder balls on a connection pad, on which flux was printed.
(3) A process to reflow to form solder bumps from solder balls.
In the process to mount solder balls mentioned above on a connection pad, a mask for arraying balls, which has an opening in the opposite position to the connection pad, is mounted on a printed circuit board, and solder balls are dropped on the connection pad using squeegees. However, with a method using squeegees, when solder balls have smaller diameters than sand grains with a diameter of 200 μm, the quality of the printed circuit board is lowered because of the variation in height of solder bumps.
Therefore, the inventor, in Japanese published unexamined application No. 2006-73999, suggested a solder ball mounting device for mounting solder balls, wherein a cylindrical member for sucking in air is used to gather air below the cylindrical member by negative pressure, the cylindrical member is moved to send solder balls to a mask for arraying balls and to drop them on a connection pad below an opening of the mask for arraying balls. The entire content of this application is incorporated herein by reference.